1. Field of the Invention
The present invention relates to an ultrasonic cleaning system equipped with degassing means, and more particularly to such an ultrasonic cleaning system which permits circulation of cleaning liquid through the system, still allowing its cleaning vessel to have two distinct zones, one being kept at such an appropriate temperature as has an effect on the degassing of the cleaning liquid, the other being kept at such an appropriate temperature as has an effect on the cleaning of an object to be put in the cleaning vessel.
2. Description of the Prior Art
The applicant field a patent application, claiming a patent to an ultrasonic cleaning apparatus equipped with degassing means. In the ultrasonic cleaning apparatus proposed therein, the cleaning liquid is subjected to degassing process in an attempt to enhance cavitation in the cleaning bath. At the time of radiation of ultrasonic waves into the cleaning bath there will be caused drastic decrease of pressure in selected places in certain conditions, and then the liquid pressure is decreased below saturated vapor pressure so that bubbles will appear in the bath. These vapor pockets will enlarge and then collapse to generate extraordinary high pressure. Such cavitation can be enhanced by degassing the cleaning liquid.
The applicant found that the proposed ultrasonic cleaning apparatus has a good cleaning effect per unit time. Specifically, it requires shotened cleaning time to remove dirt or filth from an object, compared with an ultrasonic cleaning apparatus equipped with no degassing means. The proposed ultrasonic apparatus has a boiling vessel as degassing means downstream of the cleaning vessel, and a vapor vessel downstream of the boiling vessel. Also, the proposed ultrasonic apparatus has a collection vessel upstream of the cleaning vessel, and a vapor-condenser and a water-separator upstream of the boiling vessel.
In operation, cleaning liquid which contains gas is continuously supplied from the vapor vessel to the boiling vessel after passing through the vapor-condenser tubes and the water-separator. The boiling vessel will deprive the cleaning liquid of impurities whose boiling points are than the boiling point of the cleaning liquid, and then, the cleaning liquid which contains possible least solute components will return to the cleaning vessel. Continuous repetion of this process will assure that the cleaning vessel is filled with the cleaning liquid which is degassed to its limit.
Then, the oscillator is used to generate and radiate ultrasonic waves into the cleaning bath to cause the cleaning bath to decrease in pressure until it reaches the saturated vapor pressure at the liquid temperature, and then the liquid bath will have eruptions to cause cavities to appear in the bath. Thus, the cavitation will be most likely to be caused. The study of the proposed ultasonic cleaning apparatus revealed that it would be ideal if the cleaning bath has a relatively thigh-temperature zone in its upper part and a relatively low-temperature zone in its lower part, and that the relatively low-temperature zone has an increased cleaning effect. This was not realized in designing the proposed ultrasonic cleaning apparatus.